Fluidic signal generator

ABSTRACT

A free fluid stream is established between a supply nozzle and a receiving nozzle. A hollow needle is fixedly mounted at one end and projects through the stream to define a cantilevered spring beam. The needle is offset slightly from the stream axis. A solid rod corresponding to the internal diameter of the needle is adjustably positioned within the hollow needle to control the spring characteristic. The hollow needle is deflected by the stream and returned into interfering relationship by the energy stored in the needle and internal rod to produce a periodic mechanical motion and a time varying fluidic output signal of a periodic wave form at the receiving nozzle.

Velicer et al.

[ July 17, 1973 FLUIDIC SIGNAL GENERATOR lnventors: Wencel J. Velicer, New Berlin;

Ramesh Krishnaiyer, Cudahy; Michael B. McLean, Whitefish Bay; Donald J. LaMore, Jr., Wauwatosa, all of Wis.

Assignee: Johnson Service Company,

Milwaukee, Wis.

Filed: July 29, 1971 Appl. No.: 167,213

US. Cl l37/624.14, 137/83, 137/830 Int. Cl. 605d 16/06 Field of Search 137/815, 83, 624.14;

I 235/201 ME References Cited UNITED STATES PATENTS 9/1967 Groebcr 137/815 1/1970 Palmer 137/624.14

Pressure 7/1969 Taplin et al 137/624.l4 X 7/1966 Boothe 137/8l.5 X

Primary Examiner-Alan Cohan Assistant ExaminerGerald A. Michalsky Attorney-Andrus, Sceales, Starke & Sawall [57] ABSTRACT A free fluid stream is established between a supply nozzle and a receiving nozzle. A hollow needle is fixedly mounted at one end and projects through the stream to define a cantilevered spring beam. The needle is offset slightly from the stream axis. A solid rod corresponding to the internal diameter of the needle is adjustably positioned within the hollow needle to control the spring characteristic. The hollow needle is deflected by the stream and returned into interfering relationship by the energy stored in the needle and internal rod to produce a periodic mechanical motion and a time varying fluidic output signal of a periodic wave form at the receiving nozzle.

11 Claims, 5 Drawing Figures Output FLUIDIC SIGNAL GENERATOR BACKGROUND OF THE INVENTION This invention relates to a fluidic signal'generating apparatus and particularly to such apparatus for providing a time varying output signal of a periodic wave form.

Fluidic signal generators or oscillators are widely employed in switching and control circuits or systems to provide a related clock or signal switching control. The clock produces a continuous periodic signal of a prescribed or fixed frequency, the output of which is used to produce synchronized operation within the circuit. Signal generators may be required for testing of different devices and preferably employ sinusoidal wave forms having a variable amplitude and frequency.

Although such devices are readily available for electronic and electrical systems, the recent development of fluidic devices which function as fluidic amplifying and modulating devices has given rise to a need for a fluidic means which will produce a time varying output signal of a periodic wave form. Thus, synchronous sequential fluidic logic systems are available which require incorporation of a clock oscillator generating a continuous periodic signal at a prescribed frequency. Although in the latter application the wave shape of the signal is not of prime consideration, the oscillator must have a high degree of frequency stability. Further, under normal operating conditions the frequency should be independent of variations in power supply temperature and other environmental parameters and conditions. Fluidic signal generators more particularly form a fundamental tool in the design and research of fluidic devices, circuits and systems. In such applications the fluidic signal generator preferably produces a nearly sinusoidal wave and also includes a relatively convenient and reliable system for varying the amplitude and/or frequency.

Various fluidic clock and signal generators have been suggested. For example, a rotating wheel having a plurality of teeth to periodically interrupt a jet stream, and thereby produce a periodic signal, has been suggested. Alternatively, relative movement between the input and output of a stream nozzle arrangement will produce a periodic fluidic signal. In addition various driven devices such as a piezoelectric flapper valve and nozzle as well as other fluid or flueric oscillators have been suggested.

Although time varying signal generating means for fluidic devices are therefore available, none have been found to provide the desired stability of operation with varying parameters nor do such known devices produce the desired sinusoidal wave form. Further, existing clock devices applicable to fluidic systems have been limited to a relatively low frequency range; generally operating to a maximum frequency of 500 hertz. Fluidic devices, however, can respond to frequencies well over 500 hertz and consequently present fluidic clock devices are inadequate.

SUMMARY OF PRESENT INVENTION The present invention is particularly directed to an essentially pure fluidic device for generating time varying output signals of a periodic wave formwith a highly improved stability of operation in the presence of the normal variations in parameters encountered in fluidic systems. The output may provide a highly sinusoidal fluidic signal with adjustment of the frequency and amplitude over a wide range. The frequency of the signal may be of a much higher order than those heretofore provided.

Generally, in accordance with the present invention, a jet fluid stream is established by a stream forming means and when a fluid output signal is desired is aligned with respect to a fluid receiving or sensing means. A stream impeding mechanical means or unit is resiliently mounted and biased into the path of the fluid stream. The unit is free to be moved from its initial position by the force of the stream. A resilient rod-like element or member located in the path of the stream and free to move somewhat laterally of the stream has produced highly satisfactory operation. In operation, the resilient element is unstable such that the element is forced laterally by the stream. This movement stores energy in the resilient member which energy tends to return the member to its initial position from which the process again repeats. Applicants have found that the unstable characteristic of the resilient mounted unit such as the rod-like member provides a time varying output signal of a periodic wave form.

In a particularly satisfactory construction, a resilient reed-like member in the form of a cantilevered spring unit is mounted in the path of the signal stream with the reed-like member laterally offset slightly from the axis of the free stream. The stream will then force the member laterally from the stream, storing energy in the spring unit. The stored energy returns the unit to the initial position from which the process again repeats.

In a highly practical and novel construction, the interrupting member includes a'hollow rod member or tube fixedly mounted in spaced relation to the stream and projecting into the stream to define a resilient cantilevered beam. A rod which is preferably solid and approximates the interal diameter of the tube is adjustably positioned within the tube. The tube is deflected laterally of the stream and returned into interfering relationship by the energy stored in the tube and internal rod. Generally, the frequency of oscillation is determined by the resonant frequency of the interrupting member and thus is directly related to the geometrical dimensions and physical properties of the member. Further, the frequency varies directly with the length of the internal rod within the tube. In the embodiment shown, the frequency decreases as the rod is extended outwardly of the free end of the tube and increases as the rod is retracted into and downwardly through the tube. This provides a very simple, inexpensive and reliable means of varying the frequency of the signal.

Applicants have found that the generating means of the present invention establishes a signal which is very nearly a sine wave of a constant frequency for any given construction and positioning of the interrupting member. The frequency is essentially independent of reasonable fluctuations in the power supply of the signal stream and/or the ambient temperature conditions. Further, the device has been found to permit generation of frequencies in excess of one thousand hertz with adjustment of the frequency over a relatively wide range.

The amplitude of the output may be controlled not only by the geometry of the device but by controlling of the supply pressure, the input impedance of the drive device and the like. Further the total system is essentially a fluidic powered device which does not rely on electrical or other power source for maintaining the time varying signal or movement of the interrelationship-between the control and the main stream.

In the broadest aspect of the present invention, the device could function as a mechanical signal generator. Thus, the movement of the reed or cantilever assembly which is controlled by the stream might be detected through a photoelectric means or the like.

The present invention thus provides a simple reliable relatively extensive fluid signal control device.

BRIEF DESCRIPTION OF THE DRAWING The drawing furnished herewith illustrates a preferred construction of the present invention in which the above advantages will be readily understood from the following description.

FIG. 1 is a side elevational view of a fluid signal generating device establishing a time varying output signal of a periodic wave form and having means for adjusting the frequency of the output signal;

FIG. 2 is a horizontal section taken generally on line 2-2 of FIG. 1;

FIG. 3 is a vertical section taken generally on line 3-3 of FIG. 1; I

FIG. 4 is a graphical illustration showing the adjustable frequency characteristic of the signal generating unit shown in FIGS. 1 3; and

FIG. 5 is a diagrammatic view showing an alternative construction.

DESCRIPTION OF ILLUSTRATED EMBODIMENT Referring to the drawings and particularly to FIG. 1, the present invention is shown providing a fluid signal generating device including a main or supply nozzle 1 connected to a suitable fluid supply 2. The fluid supply is preferably an adjustable pressurized source establishing a source of pressurized fluid such as air or the like, although any fluid may be employed. The supply nozzle includes an orifice 3 which in cooperation with the pressurized supply defines a predetermined stream 4 which moves in a rectilinear path through a free space or environment to a collector or receiving nozzle 5, which is mounted and coaxially aligned in spaced relationship to the nozzle 1. The collector nozzle 5 includes an orifice 6 in coaxial aligned relationship with the nozzle l for collecting and sensing of the strength of stream 4 and transmitting such sensed stream as a pressure signal to a unit 7 such as a suitable output load signal transmitting unit or the like. In the illustrated embodiment of the invention, the nozzles 1 and 5 are mounted in proper supported relationship by a pair of L-shaped supports 8 and 9 which may be interconnected as part of any suitable fixture.

In accordance with the present invention, a stream impeding means or unit 10 projects into the, path of the stream 4 and tends to impede the flow of the stream 4 from supply orifice 3 to the collecting orifice 6. In the illustrated embodiment of the invention, the unit 10 extends through the stream path and includes a tube 11 located generally centrally between the nozzle orifices 3 and 6 and mounted to define a cantilevered beam. In the illustrated embodiment of the invention as shown in FIG. 1, the upper end of tube 11 is free while the lower end is formed with a cylindrical enlargement 12 which is clamped within a suitable mounting bracket 13 between the mounting supports 8 and 9. The enlargement.l2 includes a boss or stepped portion I4 which essentially is inflexible and consequently provides the fixed support for the corresponding lower end of the tube which however is free to deflect about point 14 with respect to the stream 4. The tube 11 is formed of a suitable spring materialsuch as a stainless steel of a relatively minute thickness. The axis 15 of the illustrated tube 11, as most clearly shown in FIG. 2, is preferably laterally offset with respect to the axis 16 of the stream 4 by a very slight amount. The assembly thus establishes an unstable condition such that the stream 4 will cause the tube 11 to deflect. The tube deflection however stores energy which is operative to return the tube to the initial position. Generally, it appears that the stream will act to deflect the tube 11 such that the main stream 4 is essentially unimpeded and will thus supply increased pressure to the collecting orifice 6. The energy stored in the spring metal causes the tube to move backwardly into the stream and, in fact, appears to return to its initial position from which the process repeats periodically.

Applicants have found that the wave form of the fluidicsignals is essentially sinusoidal, and that the frequency can be varied over a relatively wide range, as follows.

In the illustrated embodiment of the invention a control rod 17 is slidably disposed within the tube and is of a sufficient length to be extended completely through the tube 11 with the outer end extending beyond the free end of the tube 11. The rod 17 is adjustably supported through any suitable means shown as a friction clamp member 18 disposed within the enlarged supporting portion 12 of the unit 10. The illustrated rod 17 is a-solid rod formed of any suitable spring material. Applicants have found that the frequency is dependent on the distance that the solid rod is inserted into the hollow tube and that the axial position relationship provides a very accurate means for tuning of the frequency to a givenfrequency within a given range. It would appear that the result can be generally related and explained by the length square term in the basic resonant or natural frequency equation for a rod-like member. Thus the resonant frequency of a solid rod is generally defined by where f frequency Y Young's modulus K radius of gyration of cross sectional area p density of material l= lengthof rod C constant FIG; 4 is a graphical illustration of the frequency variation in hertz for various axial position of the solid rod 15 relative to the tube 11. The position shown along the X-axis is the distance by which rod 17 projects out of the free end of the tube 11, with the negative values indicating that the free end of the rod 17 is retracted into the tube and spaced inwardly from its free end. As the rod is projected outwardly beyond the tube, the frequency decreases. In contrast when it is drawn into the tube the frequency increases. This, of course, conforms to the anticipated result as predicated by the equation wherein the length factor is-in the denominator and the frequency varies with the length.

In an actual construction of the device the tube was formed of a spring stainless steel with the deflection length of approximately 1% inch as measured from the fixed point 14. The outside diameter of the stainless steel tube was essentially 0.032 inches with a wall thickness of 0.006 inches to define an inside diameter of essentially 0.020 inches. The inner tuning rod was formed of a fine music wirewhich is of course an excellent spring steel. The tuning rod had a length in excess of 1% inches so as to permit extension beyond the x 0 position and had an outside diameter of 0.016 inches such that it freely moved within the needle member or tube. The frequency versus rod position characteristic was generally as shown in FIG. 4 with the frequency being tuned over a range of approximately 310 to 460 hertz.

Modification of the geometry of hollow tube 11, while maintaining the rod 17 essentially the same, resulted in a change in the range of the frequency characteristic. Thus forming of the tube with an outside diameter of 0.028 inches and of a wall thickness of 0.005 inches resulted in a frequency range of 290 to 422 hertz. Conversely, increasing the diameter of the tube member to 0.035 inches with a constant thickness of 0.006 inches produced a range of 316 to 567 hertz.

Maintaining the tube and rod diameters and thickness as given in the last example while shortening their lengths from 1% to one inches resulted in increasing the frequency range from that to a range of 565 to 1,045 hertz. Applicants have operated systems constructed in accordance with the present invention and with observed frequency variations as low as 200 and as high as 1,500 hertz. Other means of changing the frequency might of course be employed as by varying the fixed mounting position of the cantilever through an adjustable support.

The outputs were essentially a sinusoidal fluidic signal at the collector nozzle. With a supply pressure of the order of 25 pounds per square inch gauge or less a typical value of the peak-to-peak amplitude of the output signal was 1 pound per square inch gauge at a static pressure level of (0.55) pounds per square inch gauge.

The operation is very stable and reliable with the wave form and the frequency essentially independent of the power supply level and/or the ambient tempera-' ture within which the apparatus operates. For example, Applicants have operated a device constructed as a fluidic oscillator in accordance with the present invention with a supply pressure which was varied over a range of 11 to pounds per square inch gauge and at a frequency of essentially 457 hertz. The observed variation in frequency was 0.142 percent per pounds per square inch of supply pressure, which is readily recognized as an insignificant variation.

Similarly, at approximately the same frequency, the environmental temperature for the application was varied over the range from 80 to 150 Fahrenheit (F with a resulting frequency stability temperature variation of 0.006 percent per degree Fahrenheit (R). Once again, this will be recognized as an insignificant variation for practical applications.

Further, in the illustrated embodiment of the invention the output of the stream 4 is directly collected and employed as a signal stream. Any other means of sensing the strength of the stream 4 can of course be employed. For example, the stream 4 may constitute one stream of an impact modulator or may be directly interconnected to actuate a fluidic or fluid driven load device.

Also, instead of using the tube 11 and its coaxial tuning rod 17 to obtain selected output frequencies of fluidic signals, any arrangement of two contiguous cantilevers, movable with respect to each other for tuning, is within the scope of the invention. As for example, two contiguous beams slidable longitudinally with respect to each other in the path of a stream 4 for impeding the stream being received by the collector.

In addition, the cantilevers themselves need not be of resilient material, but merely resiliently mounted for movement by the force of stream 4, for example, as diagrammatically shown in FIG. 5 wherein the impeding member 19 is pivotally mounted as at 20 and resiliently urged to the impeding position by spring loaded rod unit 21 to provide a corresponding functioning. The unit 21 includes a rod 22 slidably mounted in a cylinder 23. A coil spring 24 resiliently forces the rod outwardly with the outer end abutting the impeding member 19. The device may otherwise be constructed as in the first embodiment and no further description thereof is given.

Thus, the present invention providesa fluid device which can produce, in a reliable and repeatable manner, a time varying fluid signal of a periodic wave form. As such, the structures of the invention are advantageously applicable in the systems heretofore discussed such as a fluidic clock,.signal generator and the like.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims, particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

We claim:

1. A signal generating device for producing a time varying signal comprising stream forming means to establish a free fluid stream within an environment, a stream impeding rod-like element extending substantially perpendicular through said stream and being resiliently mounted in spaced relation to said stream and urged to an initial position in the path of said stream with the center line of the rod-like element adjacent the stream and offset from the center line of the stream and laterally movable by said stream from the path of said stream as a result of the engagement with said stream for selectively producing an essentially constant stream path, and sensing means downstream of said rod-like element to detect the presence and absence of the stream.

2. The signal generating means of claim 1 wherein said sensing means includes a stream collecting orifice aligned with said stream forming means.

3. The signal generating device of claim 1 wherein said rod-like element includes a pivot support means mounted laterally offset from the axis of the fluid stream such that said stream is operative to move the member laterally from the stream path.

4. The signal generating device of claim 1 wherein said rod-like element is a resilient cantilevered spring element mounted to project into the path of said stream in an unstressed position.

5. The fluidic signal generating device of claim 4 wherein the axis of said spring element is laterally offset from the axis of said fluid stream, and a second spring element is slidably disposed contiguous to said first spring element, and a second mounting means is coupled to said second spring element to adjustably support said second spring element relative to said first spring element.

6. A signal generating device for producing a time varying signal comprising stream forming means to establish a fluid stream within an environment, and a stream impeding mechanical means resiliently mounted and urged to an initial position in the path of said stream and movable by said stream as a result of the engagement with said stream and, wherein said impeding mechanical means includes a means to vary the resiliency of the impeding member and thereby the frequency of the movement of said impeding memberv 7. A signal generating device for producing a time varying signal comprising stream forming means to establish a fluid stream within an environment, and a stream impeding mechanical means resiliently mounted and urged to an initial position in the path of said stream and movable by said stream as a result of the engagement with said stream and wherein said mechanical means includes a tubular hollow needle extending perpendicularly of the path of said stream and defining a cantilevered spring element in the path of said stream, and a second solid spring rod element slidably disposed within said needle.

8. The signal generating device of claim 7 wherein said needle is formed of a resilient spring metal, mounting means fixedly mounting a portion of said needle in spaced relation to said stream to define said cantilevered spring element projecting into the path of said stream, and said second spring rod element being of a resilient spring metal.

9. The signal generating device of claim 8 wherein said needle includes an enlarged mounting base defining said means fixedly mounting the needle.

10. The signal generating device of claim 8 wherein saidneedle is cylindrical, and said second spring element is a solid rod.

11. The signal generating device of claim 8 wherein said needle extends completely through said stream path, and said second spring element is substantially longer than the length of the needle from the mounting means to the outer end of the needle.

* a a; a 

1. A signal generating device for producing a time varying signal comprising stream forming means to establish a free fluid stream within an environment, a stream impeding rod-like element extending substantially perpendicular through said stream and being resiliently mounted in spaced relation to said stream and urged to an initial position in the path of said stream with the center line of the rod-like element adjacent the stream and offset from the center line of the stream and laterally movable by said stream from the path of said stream as a result of the engagement with said stream for selectively producing an essentially constant stream path, and sensing means downstream of said rod-like element to detect the presence and absence of the stream.
 2. The signal generating means of claim 1 wherein said sensing means includes a stream collecting orifice aligned with said stream forming means.
 3. The signal generating device of claim 1 wherein said rod-like element includes a pivot support means mounted laterally offset from the axis of the fluid stream such that said stream is operative to move the member laterally from the stream path.
 4. The signal generating device of claim 1 wherein said rod-like element is a resilient cantilevered spring element mounted to project into the path of said stream in an unstressed position.
 5. The fluidic signal generating device of claim 4 wherein the axis of said spring element is laterally offset from the axis of said fluid stream, and a second spring element is slidably disposed contiguous to said first spring element, and a second mounting means is coupled to said second spring element to adjustably support said second spring element relative to said first spring element.
 6. A signal generating device for producing a time varying signal comprising stream forming means to establish a fluid stream within an environment, and a stream impeding mechanical means resiliently mounted and urged to an initial position in the path of said stream and movable by said stream as a result of the engagement with said stream and, wherein said impeding mechanical means includes a means to vary the resiliency of the impeding member and thereby the frequency of the movement of said impeding member.
 7. A signal generating device for producing a time varying signal comprising stream forming means to establish a fluid stream within an environment, and a stream impeding mechanical means resiliently mounted and urged to an initial position in the path of said stream and movable by said stream as a result of the engagement with said stream and wherein said mechanical means includes a tubular hollow needle extending perpendicularly of the path of said stream and defining a cantilevered spring element in the path of said stream, and a second solid spring rod element slidably disposed within said needle.
 8. The signal generating device of claim 7 wherein said needle is formed of a resilient spring metal, mounting means fixedly mounting a portion of said needle in spaced relation to said stream to define said cantilevered spring element projecting into the path of said stream, and said second spring rod element being of a resilient spring metal.
 9. The signal generating device of claim 8 wherein said needle includes an enlarged mounting base defining said means fixedly mounting the needle.
 10. The signal generating device of claim 8 wherein said needle is cylindrical, and said second spring element is a solid rod.
 11. The signal generating device of claim 8 wherein said needle extends completely through said stream path, and said second spring element is substantially longer than the length of the needle from the mounting means to the outer end of the needle. 